1. Field of the Invention
The present invention relates to a humidifier for fuel cell utilizing water-permeable type hollow membranes and a process for warming the same.
2. Description of the Related Arts
A fuel cell which is carried on an automobile or such is composed of a lamination of a polymer membrane electrolyte assembly (hereinafter sometimes referred to as “MEA”) having an anode and a cathode provided on both surfaces thereof; gas passages each for supplying a reactant gas formed on both surfaces of the MEA; and separators which support MEA from both sides. In order to allow hydrogen ions for easily flowing within MEA, a humidifier is placed, which humidifies hydrogen and oxygen for being supplied within the fuel cell.
In such a fuel cell, a hydrogen gas is supplied to the anode as a fuel supply gas and air containing oxygen is supplied to the cathode as an oxidant gas, whereby a chemical energy generated due to a redox reaction between them is directly taken as an electric energy, which will be supplied to an electric motor to drive the electric motor. Specifically, at the anode side, the hydrogen gas is ionized to migrate the hydrogen ions into MEA, while electrons is migrated into MEA at the cathode to allows the electrons to be reacted with oxygen to produce water. In this series reaction, the electric energy can be taken.
The humidifier of the fuel cell has a plurality of humidification modules, which allow moisture to migrate between the supply gas supplied to the fuel cell and an exhaust gas (off gas) exhausted from the fuel cell to thereby humidify the supply gas, so that both poles, cathode and anode of the fuel, cell can be humidified.
As the prior art, we have suggested a fuel cell system, filed on Jan. 23, 2002 as JP Application No. 2001-13916 corresponding to US Patent Publication No. 2002-0119356A1, description of which is incorporated herein by reference. Referring to FIG. 5, the conventional fuel cell system will be described. FIG. 5 is a drawing which shows the configuration of the conventional fuel cell system 40. As shown in FIG. 5, the conventional fuel cell system 40 is configured so that a fuel cell (hereinafter referred to as “FC”) 41 having an air supply system 42, an air exhaust system 43, a hydrogen gas supply system 44, a hydrogen gas exhaust system 45, and a cooling system 46 provided thereon.
FC 41 is a PEM type fuel cell having a configuration in which a plurality of cells, which are units of power generation, are laminated. In this FC 41, the most stable output conditions can be obtained, for example, under a temperature environment ranging from 70 to 80° C. This FC 41 has a circuit configuration that FC 41 supplies power to a battery and a driving unit of a traction motor via a device for controlling output current (not shown).
The air supply system 42 supplies air to cathode of FC 41 at a side of an inlet thereof. From upstream to downstream, the air supply system 42 has a supercharger (S/C) 42A, an intercooler (I/C) 42B, a heat exchanger (H/E) 42C, and a cathode side humidifier 42D as a water-permeable membrane type humidifier provided thereon.
The air exhaust system 43 exhausts a highly wetted exhaust gas containing the produced water from a side of an outlet of cathode of FC 41.
The hydrogen gas supply system 44 supplies a hydrogen gas as the supply gas to the anode of FC 41 at the side of an inlet thereof. For this reason, the hydrogen gas supply system 44 has a hydrogen (H2) tank 44A, a heat exchanger (H/E) 44C, an ejector 44B, and an anode side humidifier 42D as a water-permeable membrane type humidifier provided thereon. Parallel to the anode side humidifier 42D, a water sucking ejector (E/J) 44 is placed inbetween a downstream of H/E 44C and a downstream of the anode side humidifier 44D.
The hydrogen gas exhaust system 45 exhausts a highly wetted anode exhaust gas, which is an excess hydrogen gas in which the produced water is contained, from the anode of FC 41 at a side of its outlet.
The cooling system 46 is configured so as to allows FC 41 to cool down to an appropriate temperature through a cooling medium circulating between FC 41 and heat exchanger 46A.
However, in the conventional fuel cell system, there is a temperature difference between the temperature of the fuel cell (FC) itself and the temperature of the supply gas, which poses a problem that the supply gas cannot supply to FC at a temperature similar to the temperature of FC. Also, in the fuel cell system, there is a large distance from a theoretical thermal efficiency, and thus, further enhancement of thermal efficiency in FC has been required.
An object of the present invention is, therefore, to provide a humidifier for fuel cell, which can enhance heat exchange to thereby warm a humidifier in an appropriate manner and to provide a process for warming such a humidifier.